diff --git a/DESCRIPTION b/DESCRIPTION
index f4b63c3a9f..be1d0d3b10 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -54,7 +54,6 @@ Suggests:
     knitr,
     mapproj,
     maps,
-    maptools,
     multcomp,
     munsell,
     nlme,
diff --git a/NEWS.md b/NEWS.md
index 1d95e88137..2bbe33847d 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -139,6 +139,11 @@
 * `stat_contour()` and `stat_contour_filled()` now warn about and remove
   duplicated coordinates (@teunbrand, #5215).
 * Improve performance of layers without positional scales (@zeehio, #4990)
+* `fortify()` for sp objects (e.g., `SpatialPolygonsDataFrame`) is now deprecated
+  and will be removed soon in support of [the upcoming retirement of rproj, rgeos,
+  and maptools](https://r-spatial.org/r/2023/05/15/evolution4.html). In advance
+  of the whole removal, `fortify(<SpatialPolygonsDataFrame>, region = ...)`
+  no longer works as of this version (@yutannihilation, #5244).
 
 # ggplot2 3.4.3
 This hotfix release addresses a version comparison change in r-devel. There are
diff --git a/R/fortify-spatial.R b/R/fortify-spatial.R
index 3e549cc23f..6fe7392a37 100644
--- a/R/fortify-spatial.R
+++ b/R/fortify-spatial.R
@@ -9,32 +9,31 @@
 #' @param ... not used by this method
 #' @keywords internal
 #' @name fortify.sp
-#' @examples
-#' if (require("maptools")) {
-#'  sids <- system.file("shapes/sids.shp", package="maptools")
-#'  nc1 <- readShapePoly(sids,
-#'    proj4string = CRS("+proj=longlat +datum=NAD27"))
-#'  nc1_df <- fortify(nc1)
-#' }
 NULL
 
 #' @rdname fortify.sp
 #' @export
 #' @method fortify SpatialPolygonsDataFrame
 fortify.SpatialPolygonsDataFrame <- function(model, data, region = NULL, ...) {
+  deprecate_warn0("3.4.4",
+    I("`fortify(<SpatialPolygonsDataFrame>)`"),
+    details = "Please migrate to sf."
+  )
+
   attr <- as.data.frame(model)
   # If not specified, split into regions based on polygons
   if (is.null(region)) {
-    coords <- lapply(model@polygons,fortify)
+    # Suppress duplicated warnings
+    withr::with_options(list(lifecycle_verbosity = "quiet"), {
+      coords <- lapply(model@polygons,fortify)
+    })
     coords <- vec_rbind0(!!!coords)
     cli::cli_inform("Regions defined for each Polygons")
   } else {
-    cp <- sp::polygons(model)
-
-    # Union together all polygons that make up a region
-    unioned <- maptools::unionSpatialPolygons(cp, attr[, region])
-    coords <- fortify(unioned)
-    coords$order <- 1:nrow(coords)
+    lifecycle::deprecate_stop("3.4.4",
+      I("`fortify(<SpatialPolygonsDataFrame>, region = ...)` is defunct'"),
+      details = "Please migrate to sf."
+    )
   }
   coords
 }
@@ -43,7 +42,15 @@ fortify.SpatialPolygonsDataFrame <- function(model, data, region = NULL, ...) {
 #' @export
 #' @method fortify SpatialPolygons
 fortify.SpatialPolygons <- function(model, data, ...) {
-  polys <- lapply(model@polygons, fortify)
+  deprecate_warn0("3.4.4",
+    I("`fortify(<SpatialPolygons>)`"),
+    details = "Please migrate to sf."
+  )
+
+  # Suppress duplicated warnings
+  withr::with_options(list(lifecycle_verbosity = "quiet"), {
+    polys <- lapply(model@polygons, fortify)
+  })
   vec_rbind0(!!!polys)
 }
 
@@ -51,6 +58,11 @@ fortify.SpatialPolygons <- function(model, data, ...) {
 #' @export
 #' @method fortify Polygons
 fortify.Polygons <- function(model, data, ...) {
+  deprecate_warn0("3.4.4",
+    I("`fortify(<Polygons>)`"),
+    details = "Please migrate to sf."
+  )
+
   subpolys <- model@Polygons
   pieces <- lapply(seq_along(subpolys), function(i) {
     df <- fortify(subpolys[[model@plotOrder[i]]])
@@ -70,6 +82,11 @@ fortify.Polygons <- function(model, data, ...) {
 #' @export
 #' @method fortify Polygon
 fortify.Polygon <- function(model, data, ...) {
+  deprecate_warn0("3.4.4",
+    I("`fortify(<Polygon>)`"),
+    details = "Please migrate to sf."
+  )
+
   df <- as.data.frame(model@coords)
   names(df) <- c("long", "lat")
   df$order <- 1:nrow(df)
@@ -81,6 +98,11 @@ fortify.Polygon <- function(model, data, ...) {
 #' @export
 #' @method fortify SpatialLinesDataFrame
 fortify.SpatialLinesDataFrame <- function(model, data, ...) {
+  deprecate_warn0("3.4.4",
+    I("`fortify(<SpatialLinesDataFrame>)`"),
+    details = "Please migrate to sf."
+  )
+
   lines <- lapply(model@lines, fortify)
   vec_rbind0(!!!lines)
 }
@@ -89,6 +111,11 @@ fortify.SpatialLinesDataFrame <- function(model, data, ...) {
 #' @export
 #' @method fortify Lines
 fortify.Lines <- function(model, data, ...) {
+  deprecate_warn0("3.4.4",
+    I("`fortify(<Lines>)`"),
+    details = "Please migrate to sf."
+  )
+
   lines <- model@Lines
   pieces <- lapply(seq_along(lines), function(i) {
     df <- fortify(lines[[i]])
@@ -108,6 +135,11 @@ fortify.Lines <- function(model, data, ...) {
 #' @export
 #' @method fortify Line
 fortify.Line <- function(model, data, ...) {
+  deprecate_warn0("3.4.4",
+    I("`fortify(<Line>)`"),
+    details = "Please migrate to sf."
+  )
+
   df <- as.data.frame(model@coords)
   names(df) <- c("long", "lat")
   df$order <- 1:nrow(df)
diff --git a/man/fortify.sp.Rd b/man/fortify.sp.Rd
index 31f6b6fe65..af1a587f5d 100644
--- a/man/fortify.sp.Rd
+++ b/man/fortify.sp.Rd
@@ -38,12 +38,4 @@
 To figure out the correct variable name for region, inspect
 \code{as.data.frame(model)}.
 }
-\examples{
-if (require("maptools")) {
- sids <- system.file("shapes/sids.shp", package="maptools")
- nc1 <- readShapePoly(sids,
-   proj4string = CRS("+proj=longlat +datum=NAD27"))
- nc1_df <- fortify(nc1)
-}
-}
 \keyword{internal}
diff --git a/tests/testthat/test-fortify.R b/tests/testthat/test-fortify.R
index 8741fac2d0..43b7adb74c 100644
--- a/tests/testthat/test-fortify.R
+++ b/tests/testthat/test-fortify.R
@@ -29,10 +29,14 @@ test_that("spatial polygons have correct ordering", {
   polys2 <- rev(polys)
   polys2_sp <- sp::SpatialPolygons(polys2)
   fake_sp2 <- sp::SpatialPolygonsDataFrame(polys2_sp, fake_data)
-  expected <- fortify(fake_sp2)
+  lifecycle::expect_deprecated(
+    expected <- fortify(fake_sp2)
+  )
   expected <- expected[order(expected$id, expected$order), ]
 
-  actual <- fortify(fake_sp)
+  lifecycle::expect_deprecated(
+    actual <- fortify(fake_sp)
+  )
 
   # the levels are different, so these columns need to be converted to character to compare
   expected$group <- as.character(expected$group)
@@ -40,6 +44,11 @@ test_that("spatial polygons have correct ordering", {
 
   # Use expect_equal(ignore_attr = TRUE) to ignore rownames
   expect_equal(actual, expected, ignore_attr = TRUE)
+
+  lifecycle::expect_deprecated(
+    # fortify() with region is defunct due to maptools' retirement
+    lifecycle::expect_defunct(fortify(fake_sp, region = "foo"))
+  )
 })
 
 test_that("fortify.default proves a helpful error with class uneval", {